/* ===== 响应式 ===== */
@media (max-width: 992px) {
    .hero-grid { grid-template-columns: 1fr; text-align: center; }
    .hero-content { max-width: 100%; }
    .hero-sub { margin: 0 auto 2rem; }
    .hero-actions { justify-content: center; }
    .hero-visual { display: none; }

    .about-grid { grid-template-columns: 1fr; gap: 3rem; }
    .footer-grid { grid-template-columns: 1fr 1fr; }

    .tech-stats { grid-template-columns: repeat(2, 1fr); }
    .cert-grid { grid-template-columns: repeat(2, 1fr); }
    .philosophy-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: fixed;
        top: 0; left: 0; right: 0; bottom: 0;
        background: rgba(6,8,16,0.98);
        flex-direction: column;
        justify-content: flex-start;
        align-items: center;
        gap: 0;
        z-index: 1001;
        list-style: none;
        margin: 0;
        padding: 5rem 2rem 2rem;
        overflow-y: auto;
    }
    .nav-links.open { display: flex; }
    .nav-links li {
        list-style: none;
        margin: 0;
        padding: 0.5rem 0;
        width: 100%;
        text-align: center;
        flex-shrink: 0;
    }
    .nav-links a {
        display: block;
        padding: 0.75rem 0;
        font-size: 1.15rem;
        font-weight: 500;
    }
    .nav-links a::after { display: none; }
    .nav-links .nav-cta {
        margin-top: 0.5rem;
        padding: 0.85rem 2.5rem;
        font-size: 1rem;
        display: inline-block;
    }
    .mobile-toggle { display: flex; z-index: 1002; }
    .mobile-toggle.open span:nth-child(1) { transform: rotate(45deg) translate(5px,5px); }
    .mobile-toggle.open span:nth-child(2) { opacity: 0; }
    .mobile-toggle.open span:nth-child(3) { transform: rotate(-45deg) translate(5px,-5px); }
    .mobile-overlay {
        display: none;
        position: fixed;
        inset: 0;
        background: rgba(0,0,0,0.5);
        z-index: 1000;
    }
    .mobile-overlay.open { display: block; }

    .about-stats { grid-template-columns: repeat(3, 1fr); gap: 0.75rem; }
    .about-stat { padding: 1rem; }
    .about-stat-num { font-size: 1.2rem; }

    .services-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 2rem; }

    .tech-stats { grid-template-columns: repeat(2, 1fr); gap: 1rem; }
    .tech-grid-container { grid-template-columns: 1fr; }
    .cert-grid { grid-template-columns: repeat(2, 1fr); gap: 1rem; }
    .philosophy-grid { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
    .about-stats { grid-template-columns: repeat(3, 1fr); }
    .hero-actions { flex-direction: column; align-items: center; }

    .tech-stats { grid-template-columns: repeat(2, 1fr); }
    .cert-grid { grid-template-columns: 1fr; }
}